1. Field of the Invention
The present invention relates to an improvement of a resin mold semiconductor device wherein one major surface of an island (i.e., a die pad) of a lead frame is exposed to the outside of a resin member, for realizing low thermal resistance.
2. Description of the Related Art
To reduce thermal resistance, a conventional resin mold semiconductor device adopts a structure wherein one major surface of an island 11a (i.e., a die pad) of a lead frame 11 is exposed to the outside of a resin member 12, as is shown in FIG. 1.
However, the resin mold semiconductor device of this structure has problems in that its final shape is likely to be distorted due to the heat treatment performed for forming the resin member 12. The distortion of the final shape is attributed to the fact that two materials having different coefficients of thermal expansion are bonded together, as in a bimetal. To be specific, the lead frame 11 (metal) and the resin member are formed of materials having different coefficients of thermal expansion.
If the final shape of the resin mold semiconductor device is distorted, it is likely that a semiconductor chip 13 sealed within the resin member 12 will have defects, such as cracks.
As described above, the conventional resin mold semiconductor device has its thermal resistance lowered, with one major surface of the island of the lead frame being exposed to the outside of the resin member, but the resin mold semiconductor device has problems in that its final shape is likely to be distorted due to the heat treatment performed for forming the resin member.